From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.33) id 1BopHd-0000Hw-Er for qemu-devel@nongnu.org; Sun, 25 Jul 2004 16:07:45 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.33) id 1BopHc-0000HK-Fk for qemu-devel@nongnu.org; Sun, 25 Jul 2004 16:07:45 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.33) id 1BopHc-0000Go-A2 for qemu-devel@nongnu.org; Sun, 25 Jul 2004 16:07:44 -0400 Received: from [38.113.3.71] (helo=twix.hotpop.com) by monty-python.gnu.org with esmtp (Exim 4.34) id 1BopEH-000748-VW for qemu-devel@nongnu.org; Sun, 25 Jul 2004 16:04:18 -0400 Received: from phreaker.net (kubrick.hotpop.com [38.113.3.103]) by twix.hotpop.com (Postfix) with SMTP id 8323E102432B for ; Sun, 25 Jul 2004 19:43:05 +0000 (UTC) Received: from jbrown.mylinuxbox.org (pcp03144805pcs.midval01.tn.comcast.net [68.59.228.236]) by smtp-2.hotpop.com (Postfix) with ESMTP id 1FE2672BA60 for ; Sun, 25 Jul 2004 19:14:59 +0000 (UTC) Date: Sun, 25 Jul 2004 16:03:11 -0400 From: "Jim C. Brown" Subject: Re: [Qemu-devel] qemu-fast kernel patch question Message-ID: <20040725200311.GA23104@jbrown.mylinuxbox.org> References: <410280F2.4020809@optusnet.com.au> <200407250737.44458.a_mulyadi@softhome.net> <4103174F.5040907@optusnet.com.au> <200407251401.09826.a_mulyadi@softhome.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On Sun, Jul 25, 2004 at 12:24:16PM +0200, Johannes Martin wrote: > Hi, > > Here's a quote from qemu-tech.html: > --- > 2.10 MMU emulation > > For system emulation, QEMU uses the mmap() system call to emulate the > target CPU MMU. It works as long the emulated OS does not use an area > reserved by the host OS (such as the area above 0xc0000000 on x86 > Linux). > --- > > As far as I understand this, the qemu kernel patch makes the guest kernel > use a different reserved area than the linux host. So it shouldn't matter > which kernel I apply the patch to, right? If I patch the (linux) host > kernel, I should be able to boot any unpatched (linux) guest kernel, if I > don't patch the (linux) host kernel, I have to patch my (linux) guest > kernels. Or do we need a patch-aware qemy-fast to run on a patched host? > > Assuming that OS XYZ does not use the area around 0xc0000000, it should > work inside qemu-fast, right? And if it does use that area, it should work > inside qemu-fast on a patched host? > > Maybe one of the wizards could clarify this... > > Thanks > Johannes > You could patch the host not to use that area, but then it would have to use another area ... thus you'd have to patch the guest anyways, regardless of the host. Fabrice has said that the eventual idea is to have qemu-fast detect which areas are not accessable via mmap() and use the softmmu to emulate for only those areas. The rest would be accessed via the faster mmap(). So, if you patch qemu-fast in the right way, you might not have to patch the guest or the host. :) > > _______________________________________________ > Qemu-devel mailing list > Qemu-devel@nongnu.org > http://lists.nongnu.org/mailman/listinfo/qemu-devel > -- Infinite complexity begets infinite beauty. Infinite precision begets infinite perfection.